Cross-linked polyesters of dicyclopentadiene dicarboxylic acids



United States Patent 2,87 0,112 'CROSSEIWKED PGUY'ESTERS-OF 'DI'CYCEO- PENTADIENE DICARBQXYIZIC ACIDS Joseph Kern Mertzweiller,Baton Rouge, -La., .assignor to Esso Research andEngineering'Company, a corporation ofDe'laware No Drawing. Application Marc-h 1, 1956 "SerialNo. 568,940

This invention relates to synthetic resins and-particularly to suchresins derived from dicyclopentadiene dicarboxylic acid compounds. vThe present invention further relates to new and useful modifiedpolyester resins obtained by reacting dicyclopentadiene dicarboxylic acids, alkyl derivatives of said acids or partially hydrogenated derivatives of said acidswith dihy'd-ric alcohols, diamines or amino alcoholsandcross-linking the product formed with a minor proportion of an organic diisocyanate' or diisothiocyanate. p

In an'embodiment of the-invention, about] to El -parts "by. weight of a dicyclopentadiene =dicarboxy1ic acid are mixed with about 0.1 to 5.0 parts byweight of'a C 6 glycol, for example, about 0.75 to 1.2 moles of the acid per mole of gycol, and the resulting mixture isi blended withaboutSto 30 weight percent based on-total-composition of an organic diisocyanate. .Iheblend'formedis then heated at a temperature between about 250 to 500 F., advantageously 265' to-450 F., preferably-280 to 400 F. forabout 0.5 to 20 hours or more wherebyte produce a hard, improved, new and useful modified resinous poly- In a preferred embodiment of the invention, the

ester. acid is condensed with the glycol at temperatures between about 325 to 400 F. andiithe productgformeds cross-linked at temperatures between about 265310 325 F. with the organic diisocya'nate thereby substantially pre-,.

cluding reaction products of the-monomer with thedi-' isocyanate.

Dicyclopentadiene dicarboxylic acid and other dialkyl homologues of this acid may be prepared from cyclopentadiene. Commercially,-cyclopentadiene, which is a valuable polymerization monomer, can be separated from a commercial petroleum fraction of C olefins and diolefins by heating the .mixture under such conditions of heat I andpressure astoconvert substantially all of the cyclo-a form, chiefly dicyclopenta diene, without appreciably affecting the other unsatupentadiene to polymeric rated constituents thereof. Distillation .-of the lower boiling components of this partially polymerized mixture then gives a residue consisting largely of dicyclopentadiene and minor amounts of the dimers and codimers of other.

unsatur'a'te's in the original mixture-together with minor amounts of higher polymers aand copolymers of cyclopentadiene and other uns'aturates. -ontinued heating of this dicyclopentadiene concentrate at reflux, which temperature of course will be approximately the boiling point of dicyclopentadiene, resultsintdepolymerization of substantially allot the dicylopentadiene and distillation of the cyclopentadiene'iformed without appreciably effecting depolymerization of other dimerswand codimers in the mixture.

ethanol, isopropanol, etc.

2,870,112 Patented Jan. '20, 1959 in -th'e particles have an average size of less than 50 -microns in diameter. ple,-by mechanical means either with or without the aid Dispersion is obtained, for examof emulsifying or dispersing agents. The alcohol ac- =-tivator is substantially anhydrous alcohol, such as the Zlow molecular weight aliphatic alcohols such as methanol, Alcohols containing up to diourcarbon atoms per molecule are suitable but meth- .anol,.ethanol.or isopropanol are preferred. The alcohol 31 s employed .in relatively small amounts, that is, less than =1 molecule based on the sodium and usually in amounts :less-thanfi mol equivalent. Thealcohol serves to acativatepthe sodium ;either by removingsu'rface impurities contained thereon or by forming small quantitiesof sodif..-um,- alcoholate. ;G.assing.with: carbondioxide :is carried --,out.-at ipr essures.above-z'atinospheric,.up to 10.00 p. s. i.-'g., :iorubest yields. :Goodreactionis obtained .at 50 to 1.000 .;lbs. ;:but since the :tank pressure .ofCO as handled comzim erc-iallyii-s usually. about..90.0 vto..1000 p. s. i. g. .this latter pressure is preferred. -While qfrquent reference is .made zin-the literature zto ,the' use of gmetallic potassium I01 reacting with :the methylenengroupofcyclopentadiene so. as to form cyclo- ,p en tadienyl;,-potassillm, :no references have been found wherethecorresponding sodium salt was made bydirect reactionoisodium with cyclopentadiene. 1f sodium .is

previously; dispersed to a very finely div'ided state, preferabl having a particle size of .less than 50 microns.in..di-

eter e g by. mixing with xylene, .heating to .above :the meltingapointtof thesodium and then passing the/mixture through a high-speed colloid mill and continuing theopaeration-until {the temperature fallsbelow the solidificaon pgintofahe sodium, one obtains :thesodium -in.,a

ighly-ireactiveistat'e. With sodium in-such a1finelyidi- .yided state some reaction may vbe obtained with cyclo- Starting with cyclopentadiene or alkyl (especially dialkyl) homologues of cyclopentadiene, the corresponding pentadiene, but the reaction tends to..be relatively slow.

,Jf .toga .rnolepf gdispe rsed sodium there is added u .1 :to 2

rams. of ,anhydrous ethyl .or isopropyl alcohol so ,as to tactivate the sodium :either .by removing,--by means ,of

. .solutio n, gsur-facmimpurities or .by 'forming small quan- .,,t ities .of sodium alcoholate, immediate reaction maybe obtained ,when .a mole of monomeric cyclopentadiene is ;,,added,.to.,the,dispersed sodium. :Under these conditions .the;.cyclopentadienyl sodium is readily formed, and when jithis sodium. salt is then transferred -to a suitable pressure- ;W ith carbondioxide one obtains almost exclusively :the

:salt of thedicyclopentadiene dicarboxylic acid ,,.having aminimum of .sodium carbonate or bircarbonate present. In distinction to the use of carbon dioxide un- -.der;pressure,,.if.pne gasses the mixture of theisodium or potassium cyclopentadiene with carbon dioxide .at ;atgmosp'heri c. pressure a largeproportionof the .mixtureends y ium carbonate'or bicarbonate, giving ultimately or; yields of the: desired dicarboxylicacid.

'0 I 'lhe materials to be condensed with the foregoing acids ing agents include of solid carbon dioxide and alcohol.

dicyclopentadiene.

' repressured over a period Such materials include ethylene glycol; diethylene glycol; triethylene glycol; propylene glycol; 1,2 butanediol; 1,3 butanediol; 2,3 butanediol', trimethylene glycol; tetramethylene glycol; pentamethylene glycol; mono ethanolamine; amino butanol; amino octanol; diglycol phthalate', ethylene diamine, etc.

For the purposes of the present invention, the preferred organic diisocyanate or diisothiocyanate cross linking agents are aliphatic diisothiocyanates or especially aliphatic diisocyanates. Suitable cross-linkhexamethylene diisocyanate, hexamethylene diisothiocyanate, mor p-phenylene diisothiocyanates or diisothionates, diphenyl methane diisothiocyanate or especially diphenyl methane diisocyanate.

The following runs and examples more fully explain the present invention but are not to rinsed with approximately 100 ml. of xylene so as to wash ofi occluded sodium, and the entire mixture of dispersed sodium in xylene transferred to a one-liter flask fitted with an efiicient stirrer, thermometer, ping funnel, and reflux condenser.

To the well-stirred mixture is then added 80 g. of freshly cracked and distilled monomeric cyclopentadiene boiling at 40-41 C., representing a 20% excess of the diolefin over the sodium. Just prior to addition of the diolefin ml. of anhydrous ethanol or isopropanol. With addition of the diolefin an immediate rise in temperature is noted, and maintained within the limits of 3035 C. by means of external cooling, using it necessary, a bath composed Addition time for the diolefin is usually in the neighborhood of one hour,

dropand further stirring is continued for at least another hour at the same temperature in order to insure full reaction. The sodium changes from a dark gray powder to a volu minous precipitate having a white to alight gray appearance.

The cyclopentadienyl sodium may be reacted with alkyl halides, acid chlorides or esters of chloracetic acid to give respectively: dialkyl dicyclopentadiene, diketones of dicyclopentadiene, and his (carboxymethyl esters) of Run #2.Disdium dicyclopentadiene dicarbaxylic acid.The flask contents from run #1 are then charged to a bomb capable of withstanding pressure in excess of 1000 lbs. The bomb should be of a suitable resistant material such as stainless steel, nickel, Iconel, Monel or may be a silver-lined bomb. The bomb is fastened into a shaking machine and charged with full tank pressure of carbon dioxide which will normally be within the limits of 9004000 lbs. per sq. in. gage. When charging with carbon dioxide an immediate rise in temperature is noted and a fall in pressure in a closed system occurs indicating rapid reaction of the carbon dioxide. The system is of /2. hour to full tank pressure until no further pressure drop is noted. The mixture is then allowed to shake for a periodof approximately 12 hours, during which time the initial rise in temperature to about 60 C. may be increased by external heating to about 100? C. Additional heating is not entirely necessary in order to obtain complete reaction but does hasten be considered as limiting since they are given for the purposes of il1usthere is added to the flask one or two.

the temperature of the flask contents is the reaction time so that with heating, as little as 2 hours is sufiicient. Shorter times may be employed it better mixing is available, such as propeller or turbo mixers. At the completion of the run the excess carbon dioxide is bled off, the bomb contents dumped into a Buchner funnel, and the salt washed with light naphtha or ethyl ether in order to remove excess solvent and small amounts of polymer. There is obtained a yield of from 128 to 134 g. of product varying in color from white to a light cream color. The material has a low density and very fine particle size, exhibiting fluid flow characteristics in a dry state.

Run #3.-Dicycl0pentadiene dicarboxylic acid.-- The sodium salt prepared in run #2 is conveniently converted to the free acid by dissolving the salt in water, boiling for a few minutes and precipitating the acid by addition of dilute HCl and recovering the acid crystals by filtration. The crude product isrecrystallized from approximately 50% aqueous methanol or approximately 70% aqueous acetic acid. A perfectly white crystalline acid is obtained having a melting point of 210 C. and a neutralization'equivalcnt equal to 509 mgm. KOH/ gm. It may be represented by the following structural formula: coon 8 3/ CH 4H0 l 9/ \H/ \2 HO 0 CH HO. 0 on c n .t 5

The above reactions described in runs 1, 2, and 3 are believed to be adequately described by the following series of equations: v n

to v

' 1 3518' grams;

carborylz'c acid;Seventy-five grams of methylcylopen- .tadiene (boiling point.'73: C.) was reacted at a-temper- Jture ,ofi3'0 C. with 23' grams :of sodium dispersed in 500: ml'.. of xylene. The sodium salt was then transiferred'toa silver-linedbom'b having a capacity of11.8 liters and charged with. CO at a gage pressure. of .940#/sg.

,inch. An immediate rise in temperature and a drop in pressure occurred indicating extensive reaction. The

"bomb was .repressured and allowed to shake 'for'i3hours Without additional heating being applied.

on opening the bomb, filtering .the .solid and washing with ether, a white solid salt; was obtained weighing Decomposition of the: salt with acid and recrystallization from 70% acetic acid yielded a White acid, melting at 222-223f1having a neutralization equivalent of 452 .mgm. KOHAgm- Analysis. by combusftion gave the following:

3 Them .ercent carbon 67.12 67.72 Percent hydrogen 6. '63 6. 50

.The following equations represent the chemical re- .actions involved in this. preparation.

no g /CH \C coon Notc. Position of methyl radical '(cfl'n z-shown in above equations is not known-Withcertainty,=and:as for illustratlon Only.

PARTIALLY .HYDRCGENATED DICYCLODIENE .CARBOXYIJIC ACIDS IN POLYESTER RESINS =It is known that the dimethyl ester of dicyclopentadiene dicarboxylic acid can depolymerize to the monomeric methyl ester of cyclopeutadiene carboxylic acid when heated .tocracking temperatures of about ,above 200 C.

It hasalso beendiscovered that progressive. hydrogenation-.of .theacids of .the invention to the dihydro dicar- .boxylicacids and alkyl derivatives thereof impartsv improved stability to the. resulting acids and esters thereof and-,also-renders said acids more suitable for use in the production ofv certain polyester resins of. the invention .where the reactive compounds .and resins are subjected to. higl1 temperatures.

Arepresentativeprocess involvesmaking a cyclodienyl .sodinm. compound .as above-described, by reacting .at

pressuresof about .SOto LOOOpFS. i. g.;monomeric cyclopentadiene with very .finely divided metallic sodiumat temperaturesof about .10 to. 40 C. in .thepresenceof asmall. amount-of an anhydrous. alcohol 1 as .an activator.

The dienyl sodium compound :is then:carboxylat ed with carbon .dioxide atntemperatures .between about 30; to

C.-(i. e."60 C.) to;produce the-corresponding sodium salt of the acid. Finally-the desired carboxylic acid can beobtained from the sodium saltby addition of hydrochloric acid or the like.

Thev resulting dicyclopentadiene dicarboxylic acid .is .usually a mixture of endo and exo isomersif the carboxylation temperature isin the range of about .30 C. to.0 C. However,.i f the carboxylation is at about 5.0 to'.100 C., the product is substantially all endo isomer.

Hydrogenation of the aforementioned dicyclopenta- .dienedicarboxylic acid or of its alkyl substituted homo- .logues gives dicarboxylic .acids which are more stable and .in some respectssuperior to the original unhydro- .genated acids. For .instance, unlike the unhydrogenated acids, thecorresponding dihydrogenated compoundsform .morestablediesters of.alcohols of 1 to,l3.carbon atoms,

e. g. methyl, ethyl, isooctyl, tridecyl,etc., which may be ,distilled without cracking,decarboxylationor polymerization.

However, itis apparent that itisless expensive to omit. the hydrogenation step for those formulations where the improvedthermal stability of the hydrogenated acids isnotrequired.

The basic-raw material from which essentially all of the compounds of this invention can be derived Whether hydrogenated or unhydrogenated includes dicarboxylated dimers of cyclopentadiene, alkylrsubstituted cyclopenta- .diene and mixtures thereof. 0f:foremostpractical:im-

.portance .at present are dicyclopentadiene dicarboxylic acid, dimethyldicyclopentadiene dicarboxylic acid (which is a derivative of methylcyclopentadiene) and methyldi'cyclopentadiene dicarboxylic acid, which is a derivative of a mixture of cyclopentadiene and-methylcyclopentadiene. Also, by hydrogenating the above dicyelo 'diene acids in 'such a manner that ,one of;the double bonds originally present are saturated withhydrogen, the dihydro dicyclopentadieue 'dicarboxylic acids are formed as more fully described hereinafter. This hydrogenation can be illustrated by the following equation:

Either the dihydrogenated or the tetrahydrogenated acid may be made, depending on the amount of hydrogen allowed to react. When the hydrogenation is carried out, it

' proceeds in two distinct stages, and formation of the tetrahydrogenated acid normally does not begin until after the original acid was completely converted to the dihydroacid. Since the hydrogenation of the first doublev bond is substantially easier than the hydrogenation of the second double bond, the transition point between the two stages of the hydrogenation can bedetermi'ned by following the hydrogen pressure drop. Since it is desired to'prepare the 'dihydro acid, either the proper amount of one mole of hydrogen per mole of acid can be charged to begin with,

or an excess of hydrogen may be charged and the hydroable solvent to the reaction mixture in a quantity suflicient to dissolve the original dicarboxylic acid. Suitable solvents include alcohols such as methanol, ethanol, and isopropanol as well as other inert oxygenated solvents such as acetic acid, dioxane, ether, tetrahydrofuran, etc. The amount of solvent added may equal about to 50 times the weight of the dicarboxylic acid. The hydrogenation is carried out at temperatures between about 20 to 100 0., preferably 30 to 80 C.

The following run examplifies one method of preparing a dihydro dicyclopentadiene dicarboxylic acid:

Run #5.-Twenty-two grams (0.1 mol) of dicyclopentadiene dicarboxylic acid was dissolved in 315 grams (i. e. 400 mols) of anhydrous ethanol in a pressure bottle having a capacity of 1300 ml. and connected to a hydrogen storage tank having a capacity of 6810 ml. The free space in the system was 7625 ml. The dicarboxylic acid used was a white crystalline solid having a melting point of 210 C. and a neutralization equivalent of 509 mgm. KOH/ gm.

' One hundred milligrams of Adams PtO catalyst was added to the alcoholic solution of the acid, the air exhausted from the-bottle and the system was then filled with hydrogen to a pressure of 41 p. s. i. g. On shaking, there was an immediate absorption of hydrogen until the pressure dropped ata reduced rate indicating completion of the formation .of the dihydroacid. At the end of this reaction the reaction mixture was filtered to separate the catalyst from the. alcoholic solution and the alcohol was evaporated from the'solution on a steam bath under an atmosphere of nitrogen. The solid residue was dissolved in ml. of 50% ethanol and recrystallized. The resulting 9,10-dihydrodicyclopentadiene dicarboxylic acid product was recovered in an essentially quantitative yield in the form of snow white crystals. When tested with bromine, it showed an unsaturation corresponding to one double bond per mole of the dicarboxylic acid product. The dihydroacid remained stable when heated under a blanket of nitrogen at a temperature of 250 C. for periods of 30 minutes and more, whereas the original unhydrogenated dicyclopentadiene dicarboxylic acid tended to decarboxylate and depolymerize at temperatures as low as 200 C. This increased stability is of great importance when the acid is to be used in various high temperature reactions such as the preparation of heat resistant polyesters.

Example I Sixty one grams of ethylene glycol and 163.6 grams of the dicyclopentadiene dicarboxylic acid of run #3 were placed in a round bottom flask. The mixture was heated on an oil bath at 335 F. and stripped with natural gas. Heating was continued and the temperature raised to 365 F. over a period of 2.5 hours. The mixture was cooled to about 200 F. and then heated for an additional 2.25 hours under 2-8 mm. vacuum absolute at 33S350 F. A small flow of natural gas was employed to facilitate removal of moisture. Upon cooling under natural gas, a light amber resinous adduct was obtained which softened but did not liquefy at F. Thirty seven grams of the adduct were then mixed with 6 grams of diphenyl methane diisocyanate. The mixture was heated with mixing at 284-302 F. for about 30 minutes. Upon cooling, a hard, brittle, modified polyester resin was recovered.

Example 11 One hundred and fifty grams of the dihydro-dicyclopentadiene dicarboxylic acid of run #5 are mixed with 50 grams of 2,3 butanediol and placed in a round bottom flask. The mixture is heated on an oil bath at 350 F. and stripped withnitrogen gas. Heating is continued and the temperature raised to 375 F. over a period of 2 hours. The mixture is cooled to about 200 F. and then heated for an additional 3 hours under 4-6 mm. vacuum absolute at 345 F. :5. A small flow of nitrogen gas is employed to facilitate removal of moisture. Upon cooling under nitrogen, a resinous adduct is obtained. Twenty grams of the adduct is then mixed with 5.0 grams of p-phenylene diisothiocyanate. The mixture is heated at 300 F. for 30 minutes. Upon cooling, a hard, brittle. modified polyester resin is recovered.

The modified polyester resins of the present invention may be employed in varnishes wherein about 25-90 weight percent of a resin solvent are employed. Suitable solvents include straight run mineral spirits, naphthas, light fractions of cracked gas oils, kerosenes, gasolenes, heptane, hexane, isooctane, benzene, toluene, cyclohexane etc. This is illustrated by Example III.

Example 111 Air dried'films are drawn on mild steel panels from an equal mixture of the resin of Examples I and II with straight run mineral spirits. The mixture also contains 0.5 weight percent cobalt naphthenate. The thickness of the dried film is 1.20 mils. The properties of the air dried films containing the modified polyester resin of the invention are then compared to a conventional phthalic anhydride-glycerine resin control, during drying for drying characteristics, and after drying for hardness, water resistance, alkali resistance and grease resistance. In each instance, the surface coatings made from the modified polyester resins of the present invention derived from dicyclopentadiene dicarboxylic acid compounds were equal or superior to the surface coating prepared from the conventional phthalic anhydride-glycen'ne resin control; otherwise of the same formulation.

While there are above described a number of specific embodiments of the present invention, it is also obviously possible to produce other embodiments and various equivalent modifications and variations thereof without departing from the spirit of the invention or'the scope of the appended claims.

What is claimed is:

l. A process for preparing polyester resins useful in varnishes which comprises heating 0.75 to 1.2 moles of a dicarboxylic acid selected from the group consisting of dicyclopentadiene dicarboxylic acid, dimethyldicyclopentadiene dicarboxylic acid, methyldicyclopentadiene dicarboxylic acid, and the diand tetrahydrogenated derivatives thereof, with one mole of a C -C glycol at a temperature between about 325 to 400 F., contacting the resinous polyester product thus formed with 5 to 30 weight percent, based on the total modified resin, of a cross linking agent selected from the group consisting of organic diisocyanates, organic diisothiocyanates, and mixtures thereof, at a temperature between about 265 to 325 F., and recovering a hard, modified polyester resin product.

2. A process according to claim 1 wherein the acid is dicyclopentadiene dicarboxylic acid.

3. A process according to claim 1 wherein the acid is dimethyldicyclopentadiene dicarboxylic acid.

4. A process according to claim 1 wherein the acid is I dihydrodicyclopentadiene dicarboxylic acid.

5. A process according to claim '1 wherein the glycol is ethylene glycol.

6. A process according to claim 1 wherein the glycol is 2,3-butanediol.

7. A process according to claim 1 wherein the crosslinking agent is diphenyl methane diisocyanate.

8. process according to claiml wherein the cross linking agent is p-phenylene diisothiocyanate.

9. A varnish which comprises a modified polyester resin prepared by condensing 0.75 to 1.2 moles of a dicarboxylic acid selected from the group consisting of dicyclopentadiene dicarboxylic acid, dimethyldicyclopentadiene dicarboxylic acid, methyldicyclopentadiene dicarboxylic acid, and the diand tetra-hydrogenated derivatives thereof, with one mole of a C C glycol at 325 thus formed with 5 to weight percent, based on the total modified resin, of a crosslinking agent selected from the group consisting of organic diisocyanates, or ganic diisothiocyanates, and mixtures thereof at 265 to 325 F., said modified polyester resin being dissolved in 25 to weight percent of a hydrocarbon resin solvent to form a varnish capable of being dried into hard, waterresistant surface coating films.

10. A varnish according to claim 9 wherein the resin solvent consists of straight run mineral-spirits.

11. A varnish according to claim 9 containing a drying agent consisting of cobalt naphthenate.

12. A varnish according to claim 9 wherein the acid is dicyclopentadiene dicarboxylic acid, the glycol is ethylene glycol, and the crosslinking agent is diphcnly methane diisocyanate.

References Cited in the file of this patent 

1. A PROCESS FOR PREPARING POLYESTER RESINS USEFUL IN VARNISHES WHICH COMPRISES HEATING 0.75 TO 1.2 MOLES OF A DICARBOXYLIC ACID SELECTED FROM THE GROUP CONSISTING OF DICYCLOPENTADIENE DICARBOXYLIC ACID, DIMETHYLDICYCLOPENTADIENE DICARBOXYLIC ACID, METHYLDICYCLOPENTADIENE DICARBOXYLIC ACID, AND THE DI- AND TETRAHYDROGENATED DERIVATIVES THEREOF, WITH ONE MOLE OF A C2-C10 GLYCOL AT A TEMPERATURE BETWEEN ABOUT 325* TO 400* F., CONTACTING THE RESINOUS POLYESTER PRODUCT THUS FORMED WITH 5 TO 30 WEIGHT PERCENT, BASED ON THE TOTAL MODIFIED RESIN, OF A CROSS LINKING AGENT SELECTED FROM THE GROUP CONSISTING OF ORGANIC DIISOCYANATES, ORGANIC DIISOTHIOCYANATES, AND MIXTURES THEREOF, AT A TEMPERATURE BETWEEN ABOUT 265* TO 325* F., AND RECOVERING A HARD, MODIFIED POLYESTER RESIN PRODUCT. 